Securing a Future for the Bird of Fire

by Christie Deloria

The federally endangered Kirtland's warbler.

Photo Credit: Joel Trick, USFWS

The blackened, smoldering terrain that is left after a wildfire is often viewed as a significant environmental loss. But from an ecological perspective, fire often provides a transforming rebirth. This is especially true for the jack pine forests of the northern lower peninsula of Michigan that are home to the federally endangered Kirtland’s warbler (Dendroica kirtlandii). Not only does fire open the resin sealed cones of jack pines, but it also clears the forest canopy and bares the underlying mineral soil—creating conditions that favor healthy jack pine regeneration.

The Kirtland’s warbler is often referred to as the “bird of fire” because of its strict reliance on the fire-dependent jack pine forest for nesting. Much like the legendary Phoenix that rises from the ashes to live again, so do Kirtland’s warblers. However, what was once a fire-dominated ecosystem has changed as the need to protect homes, businesses, timber, and other assets now embedded in the jack pine landscape has required fire suppression. The story of the Kirtland’s warbler’s recovery is about working within these confines to protect these valuable resources while maintaining the unique jack pine ecosystem.

Kirtland’s warblers are finicky about where they nest. They utilize large stands of dense jack pine trees that range between 5 and 16 years of age. Picture shrubby, “Christmas tree” sized pines growing so close together that it takes some effort to walk through them. In addition to the heavy thickets of trees, the birds require interspersed treeless openings for nesting. Kirtland’s warblers nest on the ground, often on the edge of these openings with the dense foliage of intertwined tree branches camouflaging their nests. Historically, wildfires naturally regenerated this mosaic of thickets and openings ideal for Kirtland’s warbler nesting. The advent of modern forest fire suppression has brought about significantly smaller and much less frequent fires. With a decline in the amount of suitable habitat paired with brood parasitism by the brown-headed cowbird (Molothrus ater), the Kirtland’s warbler population fell to a mere 201 pairs in 1971.

The Meridian Fire burned thousands of acres of Huron-Manistee National Forest and adjoining Michigan Department of Natural Resource lands in 2010. Although the fire burned through planted Kirtland's warbler habitat, it will likely result in the creation of hundreds of acres of habitat in about six or seven years.

Photo Credit: US Forest Service

The U.S. Fish and Wildlife Service (USFWS), Michigan Department of Natural Resources (MDNR), U.S. Forest Service (USFS), The Nature Conservancy, Kirtland Community College, California University of Pennsylvania, Camp Grayling, Michigan Audubon and a number of other partners have been engaged in a nearly four decade journey to recover this rare bird. The species’ recovery program, which has focused on adaptive jack pine management, brown-headed cowbird trapping, population monitoring, public education and research, has been extraordinarily effective. Since 2001, the annual census of singing males has indicated a population well over the minimum numeric recovery goal of 1,000 pairs. This year’s census counted over 1,800 male Kirtland’s warblers. The program has also been successful at creating habitat for many other species, including white-tailed deer, wild turkey, badger, eastern bluebird, snowshoe hare, upland sandpiper, indigo bunting, and brown-thrasher.

Since the 1970s, a variety of experimental techniques including ground scarification, direct seeding, and planting seedlings in various patterns, have met variable success in restoring Kirtland’s warbler habitat. In the late 1970s and early 1980s, managers also used prescribed fire to prepare sites for re-planting after mature jack pine harvesting. Fire, however, added complexity and uncertainty to habitat management. Some years, the safe burn window was so short that only a fraction of the acreage needed for the warbler was ready for re-planting. Utilizing prescribed burning created a bottleneck and prevented agencies from reaching their Kirtland’s warbler management objectives. This method also carries some risk of fire escape and wildfire. In 1980, changing weather conditions and spot fires associated with the Crane Lake prescribed burn near Mio, Michigan resulted in the Mack Lake Fire—a wildfire that burned over 25,000 acres (10,117 ha), destroyed 44 homes, and took the life of one USFS biologist. After this tragedy, agencies nearly eliminated the use of prescribed burning in jack pine. With advances in fire science over the last 30 years, however, agencies are slowly beginning to incorporate prescribed fire back into Kirtland’s warbler management.

Although prescribed fire is re-emerging as a management tool for Kirtland’s warbler, a process of clear-cutting and manually or mechanically planting jack pine seedlings is the primary means for regenerating habitat today. Seedlings are planted in an opposing wave pattern to create the jack pine thickets and scattered openings Kirtland’s warblers prefer. Land managers also incorporate snags (dead standing trees), as well as strips and small islands of live trees during clear-cutting to mimic conditions after a wildfire. Together, the USFWS, MDNR, and USFS manage nearly 190,000 acres (76,890 ha) of jack pine habitat on a 40 to 50 year rotation for Kirtland’s warblers. Approximately 3,500 acres of jack pine are replanted annually so that 38,000 acres (15,378 ha) of suitably aged jack pine habitat is available for warbler nesting at all times. With each pair needing approximately 38 acres (15 ha) of habitat, this level of management should maintain the Kirtland’s warbler population above the recovery goal.

With the number of Kirtland’s warblers having exceeded the recovery goal for over 10 years now, discussions regarding the bird’s removal from the federal list of endangered and threatened species have began. However, in order for the species to be delisted, managers must first ascertain a way to keep management ongoing into the foreseeable future.

To address the need for continuing management, the USFWS, MDNR, and USFS have agreed to manage for the species, regardless of its status under the Endangered Species Act. A Memorandum of Understanding, signed by all three agencies in May 2011, confirms this commitment. Additionally, the National Fish and Wildlife Foundation is leading an effort to establish a Friends of the Kirtland’s Warbler non-profit group, which will help garner financial and other support to sustain intensive habitat management and other conservation actions into the future. With the initiation of these efforts, the Kirtland’s warbler recovery team is one step closer to achieving its ultimate goal—recovery.

With its current dependence on man-made plantations, is the Kirtland’s warbler still the bird of fire? Absolutely. Although fire plays a diminished role in this landscape, it will always be a part of the jack pine environment. By studying fires and the habitat they create, land managers gain valuable knowledge about how to better simulate "natural" conditions. By continuously improving and adapting our management techniques, we will sustain not only Kirtland’s warbler, but also the myriad other species that depend on the jack pine ecosystem.

Christie Deloria, a fish and wildlife biologist with the Service’s East Lansing Ecological Services Field Office, can be contacted at christie_deloria@fws.gov or 906-226-1240.